class Solution {
public:
    int subarraySum(vector<int>& nums, int k) {
        unordered_map<int,int> hash;
        hash[0]=1;

        int sum=0,ret=0;
        for(auto x:nums)
        {
            sum+=x;
            if(hash.count(sum-k))ret+=hash[sum-k];
            hash[sum]++;
        }
        return ret;
    }
};